AI model comparison
Claude Opus 5.5 vs GPT-6 Astra
Pricing, context window, benchmarks, and features compared side by side. Or skip the guesswork and send one prompt to both.
Anthropic
Claude Opus 5.5
Claude Opus 5.5 is Anthropic's flagship model for demanding reasoning, coding, and long-horizon agentic work, succeeding Claude Opus 5.
- Input / 1M
- $4
- Output / 1M
- $20
- Context
- 1M
OpenAI
GPT-6 Astra
GPT-6 Astra is OpenAI's flagship model for demanding end-to-end work.
- Input / 1M
- $10
- Output / 1M
- $50
- Context
- 1.05M
At a glance
Quick verdict
How the two models stack up on the things people ask about most.
Lower price
Claude Opus 5.5
2.5x cheaper for a typical chat
Higher intelligence score
Claude Opus 5.5
57.6 vs 52.7 on Artificial Analysis
Larger context window
GPT-6 Astra
1.05M vs 1M tokens
Newer release
Claude Opus 5.5
Released September 22, 2026
Benchmarks
Benchmark scores
Independent scores from Artificial Analysis. Higher is better.
Intelligence index
Claude Opus 5.557.6GPT-6 Astra52.7Coding index
Claude Opus 5.5Not availableGPT-6 Astra76.9Agentic index
Claude Opus 5.5Not availableGPT-6 Astra51Pricing
Claude Opus 5.5 vs GPT-6 Astra API pricing
Per-token API rates. Cheaper option highlighted.
| Metric | Claude Opus 5.5 | GPT-6 Astra |
|---|---|---|
| Input tokensPer 1M tokens | $4 | $10 |
| Output tokensPer 1M tokens | $20 | $50 |
| Cached input (read)Per 1M tokens | $0.20 | $1 |
| Cache writePer 1M tokens | $5 | $12.50 |
| Long-context pricingPer 1M tokens, for very long prompts | Same rate at any length | $20 in / $75 out above 272K |
| Web searchPer request | $0.01 | $0.01 |
What it costs in practice
Estimated cost per 1,000 requests at standard rates. Coding and long-document figures also show the cost when the input is already cached.
Chat message
2K in, 500 out
Claude Opus 5.5$18GPT-6 Astra$45Coding task
30K in, 4K out
Claude Opus 5.5$200$86 cachedGPT-6 Astra$500$230 cachedLong document summary
150K in, 2K out
Claude Opus 5.5$640$70 cachedGPT-6 Astra$1600$250 cachedSpecs
Context window and capabilities
How much each model can read, how much it can write, and what it accepts as input.
| Metric | Claude Opus 5.5 | GPT-6 Astra |
|---|---|---|
| Context window | 1M tokens | 1.05M tokens |
| Max output | 128K tokens | 128K tokens |
| Input types | File, Image, Text | File, Image, Text |
| Output types | Text | Text |
| Reasoning effort levels | Max, Extra high, High, Medium, Low | Max, Extra high, High, Medium, Low |
| Default reasoning effort | High | Medium |
| Release date | September 22, 2026 | September 4, 2026 |
Features
Supported features
API features available for each model.
| Metric | Claude Opus 5.5 | GPT-6 Astra |
|---|---|---|
| Tool calling | Supported | Supported |
| Structured outputs | Supported | Supported |
| JSON mode | Supported | Supported |
| Reasoning | Supported | Supported |
| Temperature | Not supported | Not supported |
| Stop sequences | Supported | Not supported |
| Deterministic seed | Not supported | Supported |
| Verbosity control | Supported | Supported |
Keep exploring
More on these models
Other head-to-heads, the full model page, and the alternatives list for each model.
Claude Opus 5.5View full model details- Claude Opus 5.5 vs Claude Sonnet 5.5
- Claude Opus 5.5 vs Claude Fable 5.1
- Claude Opus 5.5 vs GPT-6.1 Sol
- Claude Opus 5.5 vs Claude Opus 5
- Claude Opus 5.5 vs Claude Fable 5
- Claude Opus 5.5 vs DeepSeek V4.1 Flash
- Claude Opus 5.5 vs Muse Spark 1.3
- Claude Opus 5.5 vs GLM 5.3 Flash
- Claude Opus 5.5 vs GPT-6 Sol
- Claude Opus 5.5 vs MiMo-V2.6-Flash
- Claude Opus 5.5 vs GPT-5.6 Sol
- Claude Opus 5.5 vs Hy4 preview
- Claude Opus 5.5 vs Grok 4.7
- Claude Opus 5.5 vs GPT-6 Luna
- Claude Opus 5.5 vs DeepSeek V4 Flash 0731
- Claude Opus 5.5 vs GLM 5.3
- Claude Opus 5.5 vs Kimi K3
- Claude Opus 5.5 vs DeepSeek V4 Flash 0423
- Claude Opus 5.5 vs Step 5 Preview
- Claude Opus 5.5 vs Gemini 3.8 Flash
- Claude Opus 5.5 vs Hy3
- Claude Opus 5.5 vs Gemini 3.1 Pro Preview
GPT-6 AstraView full model details- GPT-6 Astra vs Claude Sonnet 5.5
- GPT-6 Astra vs Claude Fable 5.1
- GPT-6 Astra vs GPT-6.1 Sol
- GPT-6 Astra vs Claude Opus 5
- GPT-6 Astra vs Claude Fable 5
- GPT-6 Astra vs Muse Spark 1.3
- GPT-6 Astra vs GPT-6 Sol
- GPT-6 Astra vs GPT-5.6 Sol
- GPT-6 Astra vs Grok 4.7
- GPT-6 Astra vs GLM 5.3
- GPT-6 Astra vs Kimi K3
- GPT-6 Astra vs GLM 5.3 Flash
- GPT-6 Astra vs Gemini 3.8 Flash
- GPT-6 Astra vs DeepSeek V4.1 Flash
- GPT-6 Astra vs MiMo-V2.6-Flash
- GPT-6 Astra vs Hy4 preview
- GPT-6 Astra vs GPT-6 Luna
- GPT-6 Astra vs DeepSeek V4 Flash 0731
- GPT-6 Astra vs Gemini 3.1 Pro Preview
Our take
Claude Opus 5.5 is the smarter, cheaper flagship. It leads on the Artificial Analysis Intelligence Index (57.6 vs 52.7) and costs less than half as much per output token ($20 vs $50 per million). GPT-6 Astra still has a slightly larger context window and is the better pick if you already live in OpenAI's tooling.
FAQ
Frequently asked questions
Is Claude Opus 5.5 or GPT-6 Astra cheaper?
Claude Opus 5.5 is cheaper for a typical chat (2K input tokens and 500 output tokens). Claude Opus 5.5 costs $4 per 1M input tokens and $20 per 1M output tokens, while GPT-6 Astra costs $10 per 1M input tokens and $50 per 1M output tokens.
Which has a bigger context window, Claude Opus 5.5 or GPT-6 Astra?
GPT-6 Astra supports up to 1.05M tokens of context, compared with 1M for Claude Opus 5.5.
Is Claude Opus 5.5 smarter than GPT-6 Astra?
On the Artificial Analysis Intelligence Index, Claude Opus 5.5 scores 57.6 and GPT-6 Astra scores 52.7, putting Claude Opus 5.5 ahead. Benchmarks don't capture everything, so the best test is running your own prompts through both.
Can I use Claude Opus 5.5 and GPT-6 Astra at the same time?
Yes. Shortcut Chat sends one prompt to multiple models at once, so you can see Claude Opus 5.5 and GPT-6 Astra answer side by side and keep the better response.
Why choose? Ask both.
Send one prompt to Claude Opus 5.5 and GPT-6 Astra at the same time. Compare the answers side by side and keep the best one.